Synthetic resin containers (e.g., PET bottles) having a bottle shape including a tube-shaped mouth, a tube-shaped trunk having one end closed by a bottom, and a shoulder through which another end of the trunk is connected to the mouth have been widely used as containers used to contain a variety of content liquids, such as a seasoning including soy sauce, a beverage, a cosmetic product, shampoo, and a liquid detergent.
Such a synthetic resin container is generally produced by blow molding a preform by using pressurized air. The preform has been formed by thermoplastic resin in a bottomed tubular shape. Patent Literature 1, for example, describes a synthetic resin container produced by subjecting a bottomed tubular-shaped preform to biaxial stretch blow molding using pressurized air to stretch portions of the preform that correspond to the shoulder, the trunk, and the bottom in the axial and radial directions into a predetermined bottle shape.